A typical wireless communications system comprises a plurality of wireless communications devices exchanging data with each other. In some wireless communications systems, for example, infrastructure networks, the system may further comprise a wireless base station for managing communications between the wireless communications devices. In other words, each intra-system communication would be exchanged via the wireless base station. In other wireless communications systems, for example, mesh networks and ad hoc wireless networks, the wireless base station may be omitted, i.e. the wireless communications devices may communicate directly with each other.
The wireless communications devices may communicate with each other based upon a wireless communications protocol, for example, IEEE 802.11. The wireless communications protocol comprises a set of standard rules regulating how the wireless communications devices communicate with each other and includes functions commonly needed during communication. The wireless communications system typically supports a fixed set of wireless communications protocols that correspond to respective wireless communications device types. As a wireless communications system supports more wireless communications protocols, the overhead used to operate the communications system may increase to undesirable levels that may impact performance. For example, U.S. Patent Application Publication No. 2008/0008116 to Buga et al. discloses a communications system supporting a plurality of wireless communications protocols.
Another potential drawback to the wireless communications system supporting more than one type of wireless communications device type-protocol is the difficulty of scheduling communications in the system to avoid interference. For example, listen-before-talk approaches, such as, carrier sense multiple access/collision avoidance (CSMA/CA), may be difficult to use since each wireless communications device may not be able to hear the other wireless communications devices' communications. For scheduling of communications in the wireless communications system using these listen-before-talk approaches, the transmitting wireless communications device listens for current transmissions from other wireless communications devices in the system before transmitting its own data.
An approach to the above drawback is a request-to-send/clear-to-send (RTS/CTS) method. For example, the IEEE 802.11 g wireless communications protocol uses this approach. In the RTS/CTS approach, before initiating a transmission, a transmitting wireless communications device sends a RTS message to the wireless base station. The wireless communications device then awaits a CTS message before stating communications. In other words, the wireless base station acts as a “virtual traffic cop” at an intersection of virtual streets, the number of virtual streets determined by the number of wireless communications devices in the wireless communications system. Unfortunately, the RTS/CTS approach may increase the overhead in the wireless communications system.
The IEEE 802.16 (WIMAX) wireless communications protocol is a robust technology aimed at providing metropolitan area networks. The WiMAX wireless communications protocol may provide for: long transmission ranges in the order of kilometers, robust quality-of-service (QoS) features, and scalability. Although WiMAX wireless communications devices may be desirable for certain applications, they may not integrate easily into existing and legacy wireless communications systems. Moreover, precise scheduling of transmissions and resource allocation in the communications system may be desirable.